Lumens in the body can change in size, shape, and/or patency, and such changes can present complications or affect associated body functions. For example, the walls of the vasculature, particularly arterial walls, may develop pathological dilatation called an aneurysm. Aneurysms are observed as a ballooning-out of the wall of an artery. This is a result of the vessel wall being weakened by disease, injury or a congenital abnormality. Aneurysms have thin, weak walls and have a tendency to rupture and are often caused or made worse by high blood pressure. Aneurysms can be found in different parts of the body; the most common being abdominal aortic aneurysms (AAA) and the brain or cerebral aneurysms. The mere presence of an aneurysm is not always life-threatening, but they can have serious health consequences such as a stroke if one should rupture in the brain. Additionally, a ruptured aneurysm can also result in death.
FIG. 1 depicts a cross section 100 of a person showing certain vasculature and a catheter introduced into a femoral artery for introduction of an embolic coil for treating cerebral aneurysms according to the prior art.
One approach in treating aneurysms utilizes an occlusive wire coil and delivery system for positioning the coil in a desirable site of a blood vessel. FIGS. 2A-2C illustrate cross sectional views 200A-200C of a portion of vasculature 1 showing the introduction of an embolic coil 202 into an aneurysm 2 by user of a pusher 204.
As shown in FIGS. 2A-2C, the embolic coil 202, once deployed, forms an occluding coil structure 206 within the aneurysm 2 (see FIGS. 2B-2C). One or more embolic coils 202 may be used to form coil structure 206. When the procedure is completed, the aneurysm 2 is effectively filled, allowing increased blood flow to downstream branches of the vasculature 1, as shown in FIG. 2C.
Such embolic coils have typically been placed at a desired site within the vasculature using a catheter and a pusher. As a first step, a flexible, small diameter catheter can be guided to the target site through the use of guidewires or by flow-directed means such as balloons placed at the distal end of the catheter. Once the target site has been reached, the catheter lumen is cleared by removing the guidewire (if a guidewire has been used), and the coil is placed into the proximal open end of the catheter and advanced through the catheter with a pusher. Pushers are essentially specialized wires having a distal end that is adapted to engage and push the coil through the catheter lumen as the pusher is advanced through the catheter. When the coil reaches the distal end of the catheter, it is discharged from the catheter by the pusher into the vascular site.
Several techniques have been developed to enable more accurate placement of coils within a vessel. In one technique, the coil is bonded via a metal-to-metal joint to the distal end of the pusher. The pusher and coil are made of dissimilar metals. The coil-carrying pusher is advanced through the catheter to the site, and a small electrical current is passed through the pusher-coil assembly. The current causes the joint between the pusher and the coil to be severed via electrolysis. The pusher can then be retracted leaving the detached coil at an exact position within the vessel. It is recognized that the electrolytic release of the coil requires a period of time for the metal-to-metal joint to dissolve, so that more rapid detachment of the coil from the pusher cannot occur.
Another wire coil and delivery assembly includes embolic coils that are attached to the connector of a probe assembly by a heat releasable adhesive bond. To release the embolic coil, laser energy is transmitted through the probe for heating the connector and adhesive bond. The laser apparatus required to produce laser energy, however, is a relatively expensive solution to manufacture and make available to clinicians.
Yet a further wire coil and delivery device comprise a platinum guidewire tip attached to a stainless steel guidewire. To release the platinum guidewire tip, a positive current is applied to the stainless steel guidewire for corroding away the guidewire in the bloodstream and releasing the platinum guidewire tip. This method of detaching the guidewire tip is relatively time intensive and may prolong the duration of an artificial embolization procedure.